Under what condition is denitrification typically required at wastewater plants?

• A. When the WI DNR gives the plant a nitrogen limit.
• B. When the plant experiences carbon shortage
• C. When ammonia peaks
• D. When there is a drought

Answer: (A)

Denitrification is invoked to meet regulatory nitrogen limits by removing nitrate from the effluent. When the WI DNR sets a nitrogen limit in the plant’s discharge permit, the facility typically includes a denitrification step to lower total nitrogen and comply with that limit. Other conditions—carbon shortage, ammonia peaks, or drought—don’t by themselves trigger denitrification; carbon shortage would actually hinder the process, ammonia peaks relate to nitrification control rather than nitrogen removal per se, and drought isn’t a regulatory trigger for denitrification.